In a drilling system, high pressure fluids are sent down the bore hole through a washpipe and a drill string, and ultimately to a drill motor at the bottom of the drill string. The fluid is supplied to the motor for driving cutting tools under very high pressure. A seal is necessary at the joint between the non-rotary upper connection assembly and the rotary lower connection assembly to prevent leakage of the drilling fluid to the outside. The joint is between the upper connection assembly, which includes a housing for the stator assembly, and the lower connection assembly, which includes the rotor assembly that is affixed to and rotates with the drill string. The rotor and housing are sometimes collectively referred to as a “cartridge.” The seal for this joint is referred to as a washpipe seal.
A typical wash pipe seal assembly is shown in FIG. 1. Note that the prior art seal is housed in a lower packing nut and includes three elastomeric v-ring seals mounted on heavily machined and shaped bronze rings. The top bronze ring is ported to facilitate greasing of the seal assembly. The middle bronze ring is un-ported. The lower bronze ring defines an O-ring receptacle. Each of the bronze rings are stacked face-to-face, which define leak paths. Disadvantages of the prior art seal assembly include the potential for easy damage or deformation of the bronze rings, the existence of a leak path between adjacent rings, complex machining requirements, different bronze ring configurations that require a correct stacking order, and difficulties associated with dispersing grease evenly to each of the three elastomeric v-ring seals. If too little grease is provided, then the v-ring seals are prone to early failure. If too much grease is provided, then grease may get into the mud, which may affect mud circulation.
Still referring to FIG. 1, i.e., to the prior art seal configuration, an elastomeric v-ring seal is located in a shaped ring and is received in a receptacle defined by the upper packing nut. One disadvantage associated with the prior art seal relates to the gap between the upper packing nut and the pipe. In particular, the gap can allow for the v-ring seal to be pushed into and through the gap when the seal assembly is subjected to high pressures.
In greater detail, still referring to FIG. 1, shown is prior art washpipe seal assembly 10 for connection to an upper static connector pipe or gooseneck and a dynamic lower connector pipe or shaft 14. Prior art washpipe seal assembly 10 includes washpipe 16.
A static upper seal assembly 30 surrounds upper end of washpipe 16. Static upper seal assembly 30 includes upper packing nut 32. A lower end of upper packing nut 32 defines angular recess 42 on an inside surface. Upper ring 50 is received within upper packing nut 32. Upper ring 50 has an upper surface 52 defining an annular seal receptacle for receiving seal 58.
Upper elastomeric v-ring seal 60 is located within an annular space defined by upper ring 50 and washpipe 16. Upper elastomeric v-ring seal 60 has an inner surface 62 for engaging washpipe 16. Upper elastomeric v-ring seal 60 additionally includes a lower protrusion that is received within annular recess 42.
A dynamic lower seal assembly designated generally 70 surrounds a lower end of washpipe 16. Dynamic lower seal assembly includes lower packing nut 72. Lower packing nut 72 defines vertical wall 78 that connects an upper end and a lower end. Lower packing nut 72 additionally defines grease port 86 on vertical wall 78.
First elastomeric v-ring seal 90 defines an upper protrusion received within annular recess 82 defined by an upper end of lower packing nut 72. First elastomeric v-ring seal 90 has a downwardly protruding inside seal portion for communicating with washpipe 16 and has a downwardly protruding outside seal portion.
A first bronze spacer ring 100 is located below first elastomeric v-ring seal 90. First bronze spacer ring 100 has a vertical portion that extends between downwardly protruding outside seal portion of first elastomeric v-ring 90 and an inside surface of vertical wall 78 of lower packing nut 72. First bronze spacer ring 100 defines a horizontal portion that defines grease passageway 108 for delivering grease from grease port 86 to an area adjacent washpipe 16.
A second elastomeric v-ring seal 110 has an upper protrusion received within an annular recess of first bronze spacer ring 100. Second elastomeric v-ring seal 110 has a downwardly protruding inside seal portion for communicating with washpipe 16. Second elastomeric v-ring seal 110 also has a downwardly protruding outside seal section.
A second bronze spacer ring 120 is located below second elastomeric v-ring seal 110. Second bronze spacer ring 120 has a vertical portion between the downwardly protruding outside seal portion of second elastomeric v-ring 110 and an inside surface of vertical wall 78 of lower packing nut 72. A lower surface of a horizontal portion of second bronze ring 120 defines an annular recess. An upper surface of the horizontal portion is in sealing engagement with a lower end of the downwardly protruding outside seal portion of second elastomeric v-ring seal 110.
A third elastomeric v-ring seal 130 has an upper protrusion received within the annular recess of second bronze spacer ring 120. Third elastomeric v-ring seal 130 has a downwardly protruding inside seal portion for communicating with washpipe 16. Third elastomeric v-ring seal 130 additionally has a downwardly protruding outside seal portion.
A third bronze spacer ring 140 is located below third elastomeric v-ring seal 130. Third bronze spacer ring 140 has a vertical portion between the downwardly protruding outside seal portion of third elastomeric v-ring seal 130 and an inside surface of vertical wall 78 of lower packing nut 72. Third bronze spacer ring 140 defines a horizontal portion. A lower surface of the horizontal portion defines an annular seal receptacle 146 for receiving seal 150.